1. Field of the Invention
This invention relates to an electronic parts mounting method in which electronic parts in parts feeders are picked up by a plurality of nozzles mounted on a transfer head, and are transferred to and mounted on a board.
2. Related Art
There has been extensively used the type of electronic parts mounting apparatus for transferring and mounting electronic parts (hereinafter referred to as "chips") on a board, in which while horizontally moving a transfer head in an X-direction and a Y-direction by a moving table, a chip, stored in a parts feeder is held by vacuum suction at a lower end of a nozzle on the transfer head, and is picked up, thereby transferring and mounting at a predetermined coordinate position on the board.
There has been proposed another electronic parts mounting apparatus of this type (Japanese Patent Publication No. 3-70920) in which chips stored respectively in a plurality of parts feeders juxtaposed at a pitch are simultaneously picked up by vacuum suction respectively by not less than three nozzles mounted in a row at a pitch on a transfer head, and are transferred to and mounted on a board. This method has an advantage that a mounting efficiency is greatly enhanced since the plurality of electronic parts are simultaneously picked up at a time by not less than three nozzles.
However, a bad nozzle is liable to be produced among the nozzles on the transfer head. The term "bad nozzle" means a defective nozzle which can not properly hold the chip by vacuum suction, for example, because the nozzle is clogged or bent. Heretofore, when such a bad nozzle was produced, the use of this bad nozzle was stopped, and the chips were transferred to and mounted on the board, using only the remaining normal (proper) nozzles.
However, heretofore, when the bad nozzle was produced, predetermined programs were all changed, and all of the chips were separately picked up by the remaining normal nozzles, and were transferred to and mounted on the board. Therefore, the frequency of the pick-up operations, as well as the frequency of reciprocal movements of the transfer head between the parts feeder and the board, became much larger than that predetermined in a program, so that the mounting efficiency became poor, thus inviting a problem that the advantage of the transfer head with the plurality of nozzles could not be enjoyed.